1. Field of the Invention
The present invention relates generally to earth working tools and, more particularly, is concerned with such a tool having a working element composed of a large grain, low cobalt tungsten carbide composition with enhanced physical properties.
2. Description of the Prior Art
Many mining and construction tools employ drums, cutter chains, and the like on which are mounted a multiplicity of cutter bits. Representative of the prior art are the cutter bits disclosed in U.S. Pat. Nos. to Kniff (3,499,685), Engle et al (3 519,309), McKenry et al (3,720,273), Stephenson (4,216,832), Taylor et al (4,316,636) and Ojanen (4,497,520). In the course of operating these tools, the bits are forcibly engaged with coal and rock formations to reduce and remove the same and thus are subjected to a high degree of stress and wear. Typically, each bit has a hard, wear resistant, insert or tip which contacts the formation. Heretofore, hard tips have been composed of any one of several different grades of cemented tungsten carbide composition available from Kennametal Corporation, such as grades identified as K-6T and K-3560.
The most expensive part of the cutter bit is its hard tip. Typically, over half of the cost of the bit resides in the tip. Thus, it is highly desirable to be able to use the tip as long as possible, i.e., to maximize its useful life. Early replacement increases operating costs due to increased tool downtime and usage of replacement parts and maintenance labor. While the grades of cemented tungsten carbide composition used heretofore in mining and construction applications, such as the above-identified Kennametal K-6T and K-3560, have been highly successful, there is an ongoing need for improvements in bit construction directed toward enhancement of the physical properties of the material composing the tip, with the objective being to extend the life of the bit and thereby reduce operating costs.